Field of the Disclosure
The present disclosure relates to the field of surveillance systems for safety and security applications. A surveillance apparatus for determining a position of an object in a field of view having a radar sensor and a corresponding surveillance method are disclosed. Application scenarios include burglar, thefts or intruder alarm as well as monitoring public and private areas, inside or outside.
Description of Related Art
Optical surveillance cameras are used in many public places like train stations, stadiums, subways etc. to prevent crimes or to identify criminals after they committed a crime. Optical surveillance cameras are widely used in the retail stores for video surveillance. Other important applications are safety-related applications including the monitoring of doors, entrance areas and exits for example emergency exits. Optical security cameras and surveying systems show good performance during regular operating conditions, however, the optical surveillance cameras are prawn to visual impairments. The images of the optical surveillance cameras can be impaired by smoke, dust, fog, fire and dirt on the camera system and the like. Furthermore a sufficient amount of ambient light or additional artificial light is necessary in order to illuminate the area to be surveyed.
An optical surveillance camera is also vulnerable to attacks of the optical system, for example paint from a spray attack, stickers glued to the optical system, card-board or paper obstruction in the field of view, or simply a photograph that pretends that the expected scene is monitored. Furthermore, the optical system can be attacked by laser pointers, by blinding the camera or by mechanical repositioning of the optical system.
Radar technology can in general overcome the drawbacks of the optical cameras, since electromagnetic waves in the millimeter-wave can penetrate most of the obstructions like smoke, dust, paint, card-board and clothes. Furthermore, radar systems can be used for precise positioning of a target, wherein a radar system can be integrated or added to an optical surveillance camera to improve the performance of the surveying system in general.
By using digital beam forming the need for conventional and physically large phased-array radar antenna systems can be omitted so that a compact size of the radar surveying system can be achieved. Since radar sensors work at lower frequencies than optical systems, a compact radar system cannot achieve a high resolution to identify targets in the field of view using conventional beam forming methods.
In the related art many methods are known for determining and estimating a target direction in a field of view of a radar sensor system using maximum likelihood estimation algorithms or MUSIC algorithms, however, the known methods for estimating a position of a target in the field of view, in particular the MUSIC algorithm have a high accuracy for objects in the far field which emit uncorrelated electromagnetic signals, however, the performance of the known algorithms degrades when the signal correlation increases and the objects are disposed close to the radar sensors.
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.